1. Field of the Invention
The present invention relates to a safety mechanism, and more particularly to the safety mechanism in an automatic engraving assembly to prevent the adjusting sleeve from separation with the body in adjustment of the engraving knife such that the adjustment of the engraving knife is within a predetermined range.
2. Description of the Prior Art
A conventional engraving assembly (1) is shown in FIGS. 1, 2A and 2B. The engraving assembly (1) is equipped in a printer-like device so that an engraving knife which is used to replace an ink head of the printer is able to proceed with carving on a piece of paper (2) to present different patterns on the piece of paper (2). The engraving assembly (1) is movably connected to the printer-like device such that the engraving assembly (1) is able to move in a predetermined manner to carve patterns on the piece of paper (2). The extension of the engraving knife is proportional to the thickness of papers stacked on the paper tray so that the operator needs to adjust the extent of extension of the engraving knife. To accomplish the adjustment of the engraving knife, it is necessary to know the internal structure of the engraving assembly (1) as shown in FIG. 1.
The engraving assembly (1) includes a hollow cylindrical body (115) having a top opening, a bottom opening in communication with the top opening via a path inside the body (115) and a side opening (1150) to sequentially and outwardly receive therein a ball (114), a spring (113) and a side cap (112) which is threadingly inserted into the side opening (1150) of the body (115). Thus the ball (114) is abutted by the spring (113) to partially extend into the path of the body (115). An adjusting sleeve (109) has an extension (not numbered) to be inserted into the top opening of the body (115) to threadingly connect to an inner periphery of the path of the body (115) and a passage defined therein to receive a bearing (111), an adjusting spring (107) urging against the bearing (111), an abutting block (106) on top of the adjusting spring (107) to control the compression of the adjusting spring (107) and receiving therein bearing balls (105), a plate (104) and a magnet (103). A knife urging block (102) is extended into the adjusting sleeve (109) and the body (115) and a positioning bolt (101) is threadingly extended into the top opening of the adjusting sleeve (109) to securely retain the knife urging block (102), the magnet (103), the plate (104), the bearing balls (105), the abutting block (106) and the adjusting spring (107) inside the adjusting sleeve (109). One end of the engraving knife (not shown) is securely clamped by the bearing balls (105) and a portion of the engraving knife is extended through the bearing (111) so that the engraving knife is able to freely rotate while the engraving assembly (1) is activated. After the engraving assembly (1) is assembled, it is noted that an abutting cap (108) is extended into a side of the adjusting sleeve (109) to abut the knife urging block (102) to securely retain the knife urging block (102) (as well as the engraving knife) in position. Furthermore, the ball (114) in the body (115) is partially extended into the path inside the body (115) to position the knife urging block (102) to enhance the positioning effect to the knife urging block (102). In addition, the positioning sleeve (110) is threadingly connected to the adjusting sleeve (109) to prevent the adjusting sleeve (109) from movement.
While the engraving assembly is in application, the operator first has to adjust the extension of the engraving knife out of the body (115). To accomplish the objective, the operator loosens the positioning bolt (101) as well as the abutting cap (108) to allow the adjusting sleeve (109) to freely rotate. In this case, the rotation of the adjusting sleeve (109) drives the engraving knife to extend out of or retract into the body (115) in response to the thickness of the papers (2) in the paper tray.
After the adjustment is finished, the positioning sleeve (110) is again rotated to securely abut a side face of the body (115) to retain the relative position of the adjusting sleeve (109) to the body (115). To enhance the positioning effect to the knife urging block (102) inside the adjusting sleeve (109), the positioning bolt (101) is rotated and extended into the adjusting sleeve (109). Then the abutting cap (108) is extended into the adjusting sleeve (109) to abut an outer periphery of the knife urging block (102).
While the currently available engraving assembly (1) is adjusted, it is somewhat difficult for the operator to operate the adjustment in that:
The extent of extension of the engraving knife is not precisely controlled. The operator can only control the extent of extension of the engraving knife by visual estimate or other auxiliary tool to have the exact extension of the engraving knife.
The positioning bolt (101) extended into the adjusting sleeve (109) is to enhance the positioning effect to the knife urging block (102) inside the adjusting sleeve (109). However, when the adjusting sleeve (109) is rotated, the positioning bolt (101) is rotated as well because the positioning bolt (101) is threadingly connected to the adjusting sleeve (109). Therefore, the positioning effect to the knife urging block (102) is not as good as expected.
Sometimes, when the positioning bolt (101) is sunk inside the adjusting sleeve (109), the operator will have to depend on auxiliary tool to rotate the positioning bolt (101) to facilitate the adjustment of the engraving knife.
To overcome the shortcomings, the present invention tends to provide an improved safety mechanism to mitigate the aforementioned problems.